1. Introduction
This invention relates to improved light reflectors and to lighting fixtures comprising such reflectors. More particularly, it relates to concave shaped reflectors having multiple asymmetric reflective facets, the configuration and orientation of which facets provide more uniform light distribution through a lens of a lighting fixture.
2. Background
A typical lighting fixture, consisting of a bulb or other light emitting element, a lens and a reflector to direct light through the lens will display an uneven light intensity over the lens area. Such unevenness of light intensity frequently is undesirable, as for example in certain automotive lighting applications. Emitted light may be uneven over the lens area as a whole and/or within multiple sub-sections of the lens area. Specifically, for example, it is typical with parabolic and most fresnel reflectors that light intensity decreases with distance from the light emitting element. The lens may include surface configurations or other optical features to direct or otherwise effect the emitted light.
In U.S. Pat. No. 4,706,173 to Hamada et al a lighting apparatus is disclosed which includes a large tubular light source and a reflector having a plurality of reflective surfaces. The reflective surfaces are angularly set such that light from the light source is reflected in a predetermined direction. The "apparent width" of each adjacent reflective surface is determined as a function of the distance between the light source and the reflective surface. The result of this and the large size of the tubular light source is said to be a light display of uniform illumination. The Hamada et al lighting apparatus is said to be usable as a backlight for a liquid crystal display. A set of equations is given in Hamada et al for calculating the angles and dimensions of a series of reflective facets in a concave reflector. A concave reflector formed in accordance with such equations will have a series of reflective surfaces each of which has luminance equal to that of the others, regardless of the distance between the reflective surface and the light source. Unfortunately, however, as pointed out by Hamada et al (Column 5, lines 53-57), the light from the resulting product (as is typical for lighting units employing "fresnel" type reflectors) "will have a striped appearance in which the shining reflective surfaces 20A and the unshining surfaces 20B are arranged alternately". To overcome this problem Hamada et al suggest a diffusing plate, for example, a milky plastic plate. It is suggested that if the pitch of the reflective surface (relative the intending viewing angle) is small compared with the radius of the light source, and the reflective surface and the diffusing surface are spaced at least a predetermined distance away from each other, then the surface portions of the diffusing plate illuminated by adjoining reflective surfaces 20A will overlap each other and result in a uniform illumination. FIG. 6 is cited as an example of such arrangement of the reflective facets of the reflector but does not show the diffusing plate. Hamada et al is directed only to a large cylindrical light source and reflector.
In U.S. Pat. No. 4,799,136 to Molnar a lighting fixture is shown having an elongated concave shaped reflector containing multiple reflective facets. The angles of the facets are selected to provide uniform illumination of a remote wall surface by the lighting fixture. The concave shaped reflector includes a major length rear portion and a minor length front portion. Each such portion, which face toward each other, has multiple reflecting facet surfaces. Light is reflected from the reflector facet surfaces in the major length rear portion directly outwardly through a diffusion plate. Some of the facet surfaces on the minor length front portion reflect light through the diffusion plate, while others reflect light partially against the facets in the opposite major length rear portion of the reflector. In the Molnar lighting fixture the numerous reflecting facets have varying angles selected to provide intersecting reflections to produce an asymmetric light pattern said to provide uniform distribution of light onto a wall. As seen in FIGS. 3 and 4 of Molnar, the lighting fixture is intended to provide uniform illumination of a wall when the lighting fixture is mounted from a ceiling near the top of such wall. Light must be emitted from the diffuser plate of Molnar unevenly, such that illumination of the remote bottom of the wall is uniform with that of higher portions of the wall closer to the lighting fixture.
It is an object of the present invention to provide a reflector and a lighting fixture comprising the same having a substantially uniform illumination through a lens of such lighting fixture. This and additional objects of the invention, or of particular preferred embodiments of the invention, will be better understood from the following disclosure and discussion thereof.